How to urlencode data for curl command?


Question

I am trying to write a bash script for testing that takes a parameter and sends it through curl to web site. I need to url encode the value to make sure that special characters are processed properly. What is the best way to do this?

Here is my basic script so far:

#!/bin/bash
host=${1:?'bad host'}
value=$2
shift
shift
curl -v -d "param=${value}" http://${host}/somepath $@
1
286
7/26/2017 2:06:56 PM

Accepted Answer

Use curl --data-urlencode; from man curl:

This posts data, similar to the other --data options with the exception that this performs URL-encoding. To be CGI-compliant, the <data> part should begin with a name followed by a separator and a content specification.

Example usage:

curl \
    --data-urlencode "paramName=value" \
    --data-urlencode "secondParam=value" \
    http://example.com

See the man page for more info.

This requires curl 7.18.0 or newer (released January 2008). Use curl -V to check which version you have.

344
8/14/2017 6:41:56 PM

Here is the pure BASH answer.

rawurlencode() {
  local string="${1}"
  local strlen=${#string}
  local encoded=""
  local pos c o

  for (( pos=0 ; pos<strlen ; pos++ )); do
     c=${string:$pos:1}
     case "$c" in
        [-_.~a-zA-Z0-9] ) o="${c}" ;;
        * )               printf -v o '%%%02x' "'$c"
     esac
     encoded+="${o}"
  done
  echo "${encoded}"    # You can either set a return variable (FASTER) 
  REPLY="${encoded}"   #+or echo the result (EASIER)... or both... :p
}

You can use it in two ways:

easier:  echo http://url/q?=$( rawurlencode "$args" )
faster:  rawurlencode "$args"; echo http://url/q?${REPLY}

[edited]

Here's the matching rawurldecode() function, which - with all modesty - is awesome.

# Returns a string in which the sequences with percent (%) signs followed by
# two hex digits have been replaced with literal characters.
rawurldecode() {

  # This is perhaps a risky gambit, but since all escape characters must be
  # encoded, we can replace %NN with \xNN and pass the lot to printf -b, which
  # will decode hex for us

  printf -v REPLY '%b' "${1//%/\\x}" # You can either set a return variable (FASTER)

  echo "${REPLY}"  #+or echo the result (EASIER)... or both... :p
}

With the matching set, we can now perform some simple tests:

$ diff rawurlencode.inc.sh \
        <( rawurldecode "$( rawurlencode "$( cat rawurlencode.inc.sh )" )" ) \
        && echo Matched

Output: Matched

And if you really really feel that you need an external tool (well, it will go a lot faster, and might do binary files and such...) I found this on my OpenWRT router...

replace_value=$(echo $replace_value | sed -f /usr/lib/ddns/url_escape.sed)

Where url_escape.sed was a file that contained these rules:

# sed url escaping
s:%:%25:g
s: :%20:g
s:<:%3C:g
s:>:%3E:g
s:#:%23:g
s:{:%7B:g
s:}:%7D:g
s:|:%7C:g
s:\\:%5C:g
s:\^:%5E:g
s:~:%7E:g
s:\[:%5B:g
s:\]:%5D:g
s:`:%60:g
s:;:%3B:g
s:/:%2F:g
s:?:%3F:g
s^:^%3A^g
s:@:%40:g
s:=:%3D:g
s:&:%26:g
s:\$:%24:g
s:\!:%21:g
s:\*:%2A:g

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